1. Field of Invention
The present invention relates to a golf club comprising a head with a shaft connected therewith, said head being formed by integrating a plurality of members made of different metal into one piece by fitting the members to one another. The present invention also relates to a method for manufacturing the above-structured golf club.
2. Prior Art
Typically, a golf club consists of a shaft and a clubhead and is normally classified into three types, i.e., wood, iron and putter. Iron club head, for example, is further classified by an angle of a loft (or loft angle). Iron clubs with small loft angles (20 to 30 degrees for example) are called a long iron, while those with large loft angle (40 to 50 degrees for example) a short iron club.
Generally, iron clubs are numbered in sequence from a shorter iron to a longer iron, such as the 1st, 2nd, 3rd, 4th, 5th, 6th, 7th, 8th, 9th, PW (pitching wedge), SW (sand wedge) and LW (lob wedge) in sequence.
A clubhead of an iron club has a face at its front face for hitting a golf ball and a back on its rear face. Some of such backs have cavities, others have smoothed surfaces. Every face has an area named a sweet spot, which is an area on the face that brings about the most satisfactory result when hitting a golf ball.
So-called cavity back irons (iron clubs that have cavities at their backs) have a sweet spot larger than so-called solid back irons (iron clubs whose backs are smoothed surfaces, sometimes called muscle types). On the other hand, solid back irons are advantageous in hitting strong balls, to obtain a comparatively straight travelling of balls that are not influenced by the wind with a good spin.
For iron heads, for example, there is disclosed in paragraphs 0009 and 0011 of Japanese Patent Un-Examined Publication No.8-38657 a golf club head which comprises a head body having a hosel made of metal of the relatively large specific gravity such as steel, beryllium copper alloy or the like, a cavity provided on a back surface of the head body, and a back member made of metal of the relatively small specific gravity such as titanium, aluminum or the like, said back member being pressed into said cavity, so that it is secured to the head body.
According to such conventional art, as the head body and the back member are secured to each other by pressing the latter into the former at a normal temperature, a gap is prone to be produced in a joint surface therebetween, thus resulting in a problem of the deterioration of strength. This is due to the insufficient amount of plastic deformation that would occur when the back member is pressed into the cavity. Therefore, you had to make a thickness of the face member comparatively great, for example as thick as about 3.5 mm to ensure its strength.